1. Field of the Invention
The present invention relates to door systems for railway vehicles and, more particularly, to door systems which provide for boarding from both high and low level platforms.
2. Description of the Prior Art
Railway vehicles are often used on railroad lines having passenger stations equipped with high boarding platforms extending at the vehicle floor level and others with low level boarding platforms extending at or near ground level.
Accordingly, efforts have been made to develop door systems providing for both high and low level access. For instance, U.S. Pat. No. 5,070,794 issued on Dec. 10, 1991 to Kunst et al. discloses a multi-sectioned sliding door assembly for use with a railway vehicle having a stairwell extending downwardly from the floor of the vehicle to a lower boarding level. The sliding door assembly comprises an upper sliding door displaceable to an open position for high level boarding and a lower sliding door disposed immediately below the upper sliding door and displaceable therewith to an open position for low level boarding. The upper sliding door is supported at the top by a sliding connection to a door overhead structure. An upper threshold is secured to an upper outer section of the lower sliding door to be positioned adjacent an elevated platform of a train station. The lower sliding door is connected via a slide assembly to the railway vehicle structure in the region of the upper threshold platform. In addition, the bottom of the lower door panel is guided in a lower threshold. A stairwell platform is hingedly connected to one side of an upper horizontal plane of the stairwell for covering the same during high level boarding.
Although the door assembly of the above mentioned patent is effective for enabling both high and low level boarding operations, it has been found that there is a need for a simpler system which requires fewer adjustments.
It is therefore an aim of the present invention to provide an improved door system providing for both high and low level access.
It is also an aim of the present invention to provide a door system which is relatively simple and economical to manufacture.
Therefore, in accordance with the present invention there is provided a door system for a railway vehicle having a door opening and a stairwell extending downwardly from a vehicle floor level to a bottom end of the door opening, the door system comprising a sliding door displaceable between open and closed positions for selectively closing the door opening, a stairwell platform displaceable between a retracted position for clearing the stairwell and an extended position for covering the stairwell, and a threshold extending laterally outwardly of the sliding door substantially at the vehicle floor level, the threshold being releasably connected to the sliding door for conjoint movement therewith when the stairwell platform is in the retracted position thereof, while remaining stationary in a functional position when the stairwell platform is in the extended position thereof for allowing high level boarding.
In accordance with a further general aspect of the present invention, there is provided a door system comprising a sliding door displaceable between open and closed positions, a stairwell platform displaceable between a retracted position for clearing a railway vehicle stairwell and an extended position for covering the stairwell, and a threshold extending laterally outwardly of the sliding door substantially at the vehicle floor level, the threshold being adapted to move with the sliding door and to be made stationary in a functional position thereof by engagement of the threshold with a retainer upon positioning of the stairwell platform to the extended position thereof.
In accordance with a still further general aspect of the present invention, there is provided a lock for releasably interconnecting first and second members, said lock including a catch provided on one of said first and second members and a latch assembly provided on the other one of said first and second members, said latch assembly including a housing, a slot defined in said housing, a spring-loaded latch member mounted in said housing, said latch member having a catch engaging portion extending outwardly of said housing through said slot for movement therein, and a safety member displaceable between a first position for preventing access to the interior of said housing through said slot when said latch member is urged in engagement with said catch and a second position for at least partly clearing said slot so as to allow said latch member to be displaced to an unlocked position in which said latch member and said catch are disconnected.